propagate errors on wait(::RemoteRef) and remotecall_wait

[amitmurthy]

closes #13730

With this patch and julia -p 1:

julia> t = 0.0
0.0

julia> @sync @parallel for i=1:10
           t.nonexistent
       end
ERROR: On worker 2:
type Float64 has no field nonexistent
 [inlined code] from none:2
 in anonymous at no file:0
 in anonymous at multi.jl:1348
 in anonymous at multi.jl:899
 in run_work_thunk at multi.jl:651
 in run_work_thunk at multi.jl:660
 in anonymous at task.jl:54
 in remotecall_fetch at multi.jl:737
 [inlined code] from multi.jl:373
 in call_on_owner at multi.jl:783
 in wait at multi.jl:791
 in sync_end at ./task.jl:396

julia> pmap(x->t.nonexistent, [0,1,2])
1-element Array{Any,1}:
 RemoteException(2,CapturedException(UndefVarError(:t),Any[(:anonymous,:none,1,symbol(""),-1,1),(:anonymous,symbol("multi.jl"),902,symbol(""),-1,1),(:run_work_thunk,symbol("multi.jl"),651,symbol(""),-1,1),(:anonymous,symbol("multi.jl"),902,symbol("task.jl"),59,1)]))

julia> pmap(x->t.nonexistent, [0,1,2]; err_stop=true)
1-element Array{Any,1}:
 RemoteException(2,CapturedException(UndefVarError(:t),Any[(:anonymous,:none,1,symbol(""),-1,1),(:anonymous,symbol("multi.jl"),902,symbol(""),-1,1),(:run_work_thunk,symbol("multi.jl"),651,symbol(""),-1,1),(:anonymous,symbol("multi.jl"),902,symbol("task.jl"),59,1)]))

@parallel prints an error.

pmap returns the exception objects as before.

[JeffBezanson]

Great, thanks.

I notice that fetch (and wait) doesn't propagate exceptions if the ref is local:

julia> r = remotecall(error, 1)
RemoteRef{Channel{Any}}(1,1,6)

julia> fetch(r)
RemoteException(1,CapturedException(ErrorException(""),Any[(:error,symbol("error.jl"),22,symbol(""),-1,1),(:run_work_thunk,symbol("multi.jl"),651,symbol(""),-1,1),(:run_work_thunk,symbol("multi.jl"),660,symbol(""),-1,1),(:anonymous,symbol("task.jl"),54,symbol(""),-1,1)]))

Is that intentional? It doesn't seem to me that this should depend on the location of the ref.

[amitmurthy]

Good catch. Will fix.

[amitmurthy]

Fixed.

[JeffBezanson]

Nice.